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Energy absorption potential of concrete floors containing secondary (shrinkage and temperature) reinforcements

K. S. SIVAKUMARAN,R. M. KOROL,Xiao FAN

《结构与土木工程前沿（英文）》 2014年 第8卷 第3期   页码 282-291 doi: 10.1007/s11709-014-0269-3

摘要： This paper experimentally investigates the energy absorption potential of two types of concrete floors, namely, normal density concrete and structural low-density concrete, containing secondary (shrinkage and temperature) reinforcements. The test program considered the following secondary reinforcements: 1) traditional welded-wire steel mesh, 2) steel fiber and 3) poly composite fiber. To estimate the extent to which crushing of floor slab materials would help absorb energy, a series of concrete penetration tests employing patch loading was undertaken on scaled down model slabs. Each concrete-secondary reinforcement combination considered slabs of 50 mm in depth with square plan dimensions ranging from 50 to 500 mm, resulting in a total of 30 test specimens. The first part of the paper discusses the test specimens, the test setup, and the test procedure. The second part of the paper presents the experimental results and establishes the energy absorption of different concrete- secondary reinforcement combinations. Sieve analysis results of the crushed specimens were used to derive a “work index” value that relates the pulverized particle size distributions to energy inputs. The work index values of concrete-secondary reinforcement systems can be used to assess the energy dissipation potential associated with such floor slabs in buildings undergoing progressive collapse. The results indicate that floors with secondary reinforcements could play an important role in helping arrest global progressive collapse.

关键词： concrete floors     structural low-density concrete     shrinkage and temperature reinforcements     energy absorption     penetration tests     sieve analysis    

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An improved low-complexity sum-product decoding algorithm for low-density parity-check codes

Michaelraj Kingston ROBERTS,Ramesh JAYABALAN

《信息与电子工程前沿（英文）》 2015年 第16卷 第6期   页码 511-518 doi: 10.1631/FITEE.1400269

摘要： In this paper, an improved low-complexity sum-product decoding algorithm is presented for low-density parity-check (LDPC) codes. In the proposed algorithm, reduction in computational complexity is achieved by utilizing fast Fourier transform (FFT) with time shift in the check node process. The improvement in the decoding performance is achieved by utilizing an optimized integer constant in the variable node process. Simulation results show that the proposed algorithm achieves an overall coding gain improvement ranging from 0.04 to 0.46 dB. Moreover, when compared with the sum-product algorithm (SPA), the proposed decoding algorithm can achieve a reduction of 42%-67% of the total number of arithmetic operations required for the decoding process.

关键词： Computational complexity     Coding gain     Fast Fourier transform (FFT)     Low-density parity-check (LDPC) codes     Sum-product algorithm (SPA)    

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the ammonia oxidation capacity of ammonia-oxidizing archaeon originated from wastewater: Utilizing low-density

《环境科学与工程前沿（英文）》 2021年 第15卷 第5期 doi: 10.1007/s11783-020-1375-1

摘要：

• AOA’s ammonia oxidizing capacity was enhanced under moderate magnetic field.

关键词： Ammonia-oxidizing archaeon     Ammonia oxidation     Magnetic field     Magnetotaxis     Heredity    

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A low-density polyethylene composite with phosphorus-nitrogen based flame retardant and multi-walled

Yong Luo, Yuhui Xie, Renjie Chen, Ruizhi Zheng, Hua Wu, Xinxin Sheng, Delong Xie, Yi Mei

《化学科学与工程前沿（英文）》 2021年 第15卷 第5期   页码 1332-1345 doi: 10.1007/s11705-021-2035-0

摘要： Design and exploitation of flame retardant polymers with high electrical conductivity are desired for polymer applications in electronics. Herein, a novel phosphorus-nitrogen intumescent flame retardant was synthesized from pentaerythritol octahydrogen tetraphosphate, phenylphosphonyl dichloride, and aniline. Low-density polyethylene was combined with the flame retardant and multi-walled carbon nanotubes to form a nanocomposite material via a ball-milling and hot-pressing method. The electrical conductivity, mechanical properties, thermal performance, and flame retardancy of the composites were investigated using a four-point probe instrument, universal tensile machine, thermogravimetric analysis, and cone calorimeter tests, respectively. It was found that the addition of multi-walled carbon nanotubes can significantly improve the electrical conductivity and mechanical properties of the low-density polyethylene composites. Furthermore, the combination of multi-walled carbon nanotubes and phosphorus–nitrogen flame retardant remarkably enhances the flame retardancy of matrixes with an observed decrease of the peak heat release rate and total heat release of 49.8% and 51.9%, respectively. This study provides a new and effective methodology to substantially enhance the electrical conductivity and flame retardancy of polymers with an attractive prospect for polymer applications in electrical equipment.

关键词： MWCNTs     PEPA     electrical conductivity     flame retardant     low density polyethylene    

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Correlative investigation of copper/low-density polyethylene nanocomposite on the endometrial angiogenesis

LI Jianxiong, LIU Zilong, DUAN Yonggang, YU Jing, ZHU Changhong, LI Shuang, XIE Changsheng

《医学前沿（英文）》 2007年 第1卷 第4期   页码 401-404 doi: 10.1007/s11684-007-0078-3

摘要： The purpose of this study was to investigate the effects of copper/low-density polyethylene nanocomposite (nano-Cu/LDPE) on the endometrial angiogenesis in rats, and 100 sexual mature female SD rats were randomly divided into five groups: sham-operation groups (SO group, = 20), bulk copper groups (Cu group, = 20), LDPE groups ( = 20), nano-Cu/LDPE groups I ( = 20) and II ( = 20). The levels of angiopoietin-2 (Ang-2), its receptor (Tie-2) and CD34 of the rats endometria in each group were examined by using the S-P method of the immunohistochemistry 30 and 180 days after insertion, respectively. Compared with those in the SO group, the expression of Ang-2 and Tie-2 in all the experimental groups was obviously increased 30 days after insertion, and these parameters in nano-Cu/LDPE groups, except for Ang-2 level in nano-Cu/LDPE group II, were significantly lower in comparison with those in Cu group (<0.05). On the 180th day after insertion, Ang-2 and Tie-2 levels were still higher in Cu group and LDPE group, but there was no difference of Ang-2 and Tie-2 levels between nano-Cu/LDPE groups and the SO group (>0.05). Compared with those in the SO group, the significant increases in microvessel density (MVD) were observed on the 30th and the 180th day after the insertion of the bulk copper (<0.05). There was no significant difference in MVD counts before and after the insertion of nano-Cu/LDPE (>0.05). The results show that Nano-Cu/LDPE have slighter influence on the endometrial angiogenesis than bulk copper.

关键词： significant difference     female     endometrial angiogenesis     nano-Cu/LDPE     CD34    

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Performance of inverse fluidized bed bioreactor in treating starch wastewater

M. RAJASIMMAN, C. KARTHIKEYAN

《化学科学与工程前沿（英文）》 2009年 第3卷 第3期   页码 235-239 doi: 10.1007/s11705-009-0020-0

摘要： Aerobic digestion of starch industry wastewater was carried out in an inverse fluidized bed bioreactor using low-density (870 kg/m ) polypropylene particles. Experiments were carried out at different initial substrate concentrations of 2250, 4475, 6730, and 8910 mg COD/L and for various hydraulic retention times (HRT) of 40, 32, 24, 16, and 8 h. Degradation of organic matter was studied at different organic loading rates (OLR) by varying the HRT and the initial substrate concentration. From the results it was observed that the maximum COD removal of 95.6% occurred at an OLR of 1.35 kg COD/(m ·d) and the minimum of 51.8% at an OLR of 26.73 kg COD/(m ·d). The properties of biomass accumulation on the surface of particles were also studied. It was observed that constant biomass loading was achieved over the entire period of operation.

关键词： inverse fluidization     low-density particles     polypropylene     starch     biofilm    

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Shear assessment of compression flanges of structural concrete T-beams

Bj?rn SCHüTTE,Viktor SIGRIST

《结构与土木工程前沿（英文）》 2014年 第8卷 第4期   页码 354-361 doi: 10.1007/s11709-014-0082-z

摘要： In T-beams the force transfer from the web into the flange has to be studied. The general design procedure is based on a strut-and-tie (or a stress field) model which comprises spreading compressive and transverse tensile forces. As is known, strut-and-tie models represent the force flow within a structural member at ultimate. This procedure is sufficient for design purposes and in general, leads to safe results. For the assessment of a structure it may be worthwhile to improve the accuracy. For this purpose both web and flange have to be looked at more in detail. An advanced method for the analysis of webs in shear is the Generalized Stress Field Approach [ ]. This approach can be utilized for treating flanges, where the classical assumptions have to be adapted; in particular by considering the strain dependence of the concrete compressive strength and thus, defining a representative strain value. In the present contribution background and details of these aspects are given, and the corresponding calculation procedure is described. Theoretical results are compared with experimental data and show a reasonably good agreement. However, as the number of sufficiently documented tests is very limited no concluding findings are attained.

关键词： concrete structures     structural assessment     stress field analysis     shear    

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混凝土结构性干预所必需的材料力学性能 Article

Tamon Ueda

《工程（英文）》 2019年 第5卷 第6期   页码 1131-1138 doi: 10.1016/j.eng.2019.02.012

摘要：

结构性干预包括修复和（或）改善结构性能。除了混凝土和钢材这两种典型的混凝土结构材料外，各种纤维增强复合材料（FRP），混合纤维、聚合物和黏合剂的黏结材料也常被用于结构性干预。为了预测结构性能，有必要开发一种不仅适用于钢材，而且适用于其他材料的通用方法。这种通用模型可以提供有关改善结构性能所需的力学性能的信息。外部黏结是一种典型的结构干预方案，在新结构中没有得到应用。为了在基体混凝土和外部黏结材料的接合点上获得更好的黏结强度，我们有必要阐明材料的性能和结构细节。本文介绍基体混凝土的力学性能和相关干预材料用于以下目的：①获得更高的抗剪强度和减少构件在结构性干预后的极限变形；②使外部黏结获得更高的黏结强度。本文得出的结论是，在有结构干预的结构中，为了提高结构的力学性能，干预材料的一些力学性能和结构细节是新的，且不同于没有干预的结构。例如，在无结构性干预的结构中，高强度和高刚度是材料的重要性能，而高断裂应力和低刚度是结构干预材料的重要性能。

关键词： 结构性干预     高断裂应力     无屈服     低刚度     粗糙度     FRP 聚合物    

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Comments on “Prediction on CO uptake of recycled aggregate concrete”, Frontiers of Structural and Civil

《结构与土木工程前沿（英文）》 2021年 第15卷 第6期   页码 1504-1506 doi: 10.1007/s11709-021-0782-0

摘要： A methodology to compute the CO2 uptake of recycled aggregate concrete is proposed in the commented paper. Besides some typos in several formulas, it is found that the approach to estimate the specific surface area of the recycled aggregates is not correct. This issue has some impact in the conclusions of the commented paper. Therefore, aiming to improve the understanding, accuracy and findings of the commented paper, an alternative approach to estimate the specific surface area of the recycled aggregates, as well as an erratum of the formulas and revised conclusions are suggested.
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Design of packing cup interference fit value of hypercompressors for low density polyethylene production

Da LEI,Xuehong LI,Yun LI,Xiwen REN

《能源前沿（英文）》 2019年 第13卷 第1期   页码 107-113 doi: 10.1007/s11708-017-0450-1

摘要： The hypercompressor is one of the core facilities in low density polyethylene production, with a discharge pressure of approximately 300 MPa. A packing cup is the basic unit of cylinder packing, assembled by the interference fit between an inner cup and an outer cup. Because the shrink-fitting prestresses the packing cup, serious design is needed to gain a favorable stress state, for example, a tri-axial compressive stress state. The traditional method of designing the interference fit value for packing cups depends on the shrink-fit theory for thick-walled cylinder subject to internal and external pressure. According to the traditional method, critical points are at the inner radii of the inner and external cup. In this study, the finite element method (FEM) has been implemented to determine a more accurate stress level of packing cups. Different critical points have been found at the edge of lapped sealing surfaces between two adjacent packing cups. The maximum Von Mises equivalent stress in a packing cup increases after a decline with the rise of the interference fit value. The maximum equivalent stress initially occurs at the bore of the inner cup, then at the edge of lapped mating surfaces, and finally at the bore of the outer cup, as the interference radius increases. The traditional method neglects the influence of axial preloading on the interference mating pressure. As a result, it predicts a lower equivalent stress at the bore of the external cup. A higher interference fit value accepted by the traditional method may not be feasible as it might already make packing cups yield at the edge of mating surfaces or the bore of the external cup. Along with fatigue analysis, the feasible range of interference fit value has been modified by utilizing FEM. The modified range tends to be narrower and safer than the one derived from the traditional method, after getting rid of shrink-fit values that could result in yielding in a real packing cup.

关键词： interference fit value     packing cup     hypercompressor     finite element method (FEM)    

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Recent development in low-constraint fracture toughness testing for structural integrity assessment of

Jidong KANG, James A. GIANETTO, William R. TYSON

《机械工程前沿（英文）》 2018年 第13卷 第4期   页码 546-553 doi: 10.1007/s11465-018-0501-2

摘要：

Fracture toughness measurement is an integral part of structural integrity assessment of pipelines. Traditionally, a single-edge-notched bend (SE(B)) specimen with a deep crack is recommended in many existing pipeline structural integrity assessment procedures. Such a test provides high constraint and therefore conservative fracture toughness results. However, for girth welds in service, defects are usually subjected to primarily tensile loading where the constraint is usually much lower than in the three-point bend case. Moreover, there is increasing use of strain-based design of pipelines that allows applied strains above yield. Low-constraint toughness tests represent more realistic loading conditions for girth weld defects, and the corresponding increased toughness can minimize unnecessary conservatism in assessments. In this review, we present recent developments in low-constraint fracture toughness testing, specifically using single-edge-notched tension specimens, SENT or SE(T). We focus our review on the test procedure development and automation, round-robin test results and some common concerns such as the effect of crack tip, crack size monitoring techniques, and testing at low temperatures. Examples are also given of the integration of fracture toughness data from SE(T) tests into structural integrity assessment.

关键词： fracture toughness     constraint effect     single-edge-notched tension test     pipeline     structural integrity assessment    

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Evaluation of the static and dynamic structural performance of segmental pre-stressed concrete box girder

Ali Fadhil NASER, Zonglin WANG

《结构与土木工程前沿（英文）》 2013年 第7卷 第2期   页码 164-177 doi: 10.1007/s11709-013-0196-8

摘要： The objectives of this study are to explain the repairing and strengthening methods which are used to improve the structural performance of the bridge structure, to analyze the static and dynamic responses after strengthening, and to evaluate the performance of the bridge structure after repairing and strengthening. The methods of repairing and strengthening include reconstruction the deck of the bridge by casting 10 cm layer of concrete, strengthening the web and bottom floor of box girders of middle spans and side spans by sticking the steel plates, strengthening the whole bridge structure by using external pre-stressing tendons, and treatment the cracks. The results of theoretical analysis show that the values of tensile stress and vertical deflection are decreased and the compressive stress is increased after strengthening. There are not tensile stresses are appeared in the sections of the bridge structure. The modal analysis results show that the value of natural frequency is equal to 2.09 Hz which is more than the values before strengthening which is equal to 1.64 Hz, indicating that the stiffness of the bridge structure is improved and the strengthening process is effective to improve the cracks resistance and bearing capacity of the bridge structure.

关键词： structural performance     steel plates     external pre-stressing     cracks     grouting method     static    

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On the added value of multi-scale modeling of concrete

《结构与土木工程前沿（英文）》 2022年 第16卷 第1期   页码 1-23 doi: 10.1007/s11709-021-0790-0

摘要： This review of the added value of multi-scale modeling of concrete is based on three representative examples. The first one is concerned with the analysis of experimental data, taken from four high-dynamic tests. The structural nature of the high-dynamic strength increase can be explained by using a multi-scale model. It accounts for the microstructure of the specimens. The second example refers to multi-scale thermoelastic analysis of concrete pavements, subjected to solar heating. A sensitivity analysis with respect to the internal relative humidity (RH) of concrete has underlined the great importance of the RH for an assessment of the risk of microcracking of concrete. The third example deals with multi-scale structural analysis of a real-scale test of a segmental tunnel ring. It has turned out that multi-scale modeling of concrete enables more reliable predictions of crack opening displacements in tunnel segments than macroscopic models taken from codes of practice. Overall, it is concluded that multi-scale models have indeed a significant added value. However, its degree varies with these examples. In any case, it can be assessed by means of a comparison of the results from three sources, namely, multi-scale structural analysis, conventional structural analysis, and experiments.

关键词： experiments     multi-scale analysis     conventional structural analysis     concrete     reinforced concrete    

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Crack detection for wading-concrete structures using water irrigation and electric heating

《结构与土木工程前沿（英文）》 2023年 第17卷 第3期   页码 368-377 doi: 10.1007/s11709-022-0926-x

摘要： Cracking in wading-concrete structures has a worse impact on structural safety compared with conventional concrete structures. The accurate and timely monitoring of crack development plays a significant role in the safety of wading-concrete engineering. The heat-transfer rate near a crack is related to the flow velocity of the fluid in the crack. Based on this, a novel crack-identification method for underwater concrete structures is presented. This method uses water irrigation to generate seepage at the interface of a crack; then, the heat-dissipation rate in the crack area will increase because of the convective heat-transfer effect near the crack. Crack information can be identified by monitoring the cooling law and leakage flow near cracks. The proposed mobile crack-monitoring system consists of a heating system, temperature-measurement system, and irrigation system. A series of tests was conducted on a reinforced-concrete beam using this system. The crack-discrimination index ψ was defined, according to the subsection characteristics of the heat-source cooling curve. The effects of the crack width, leakage flow, and relative positions of the heat source and crack on ψ were studied. The results showed that the distribution characteristics of ψ along the monitoring line could accurately locate the crack, but not quantify the crack width. However, the leakage flow is sensitive to the crack width and can be used to identify it.

关键词： structural health monitoring     underwater concrete structure     fiber Bragg grating     crack detection     temperature tracer method    

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Performance evaluation of low-rise infilled reinforced concrete frames designed by considering local

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 686-703 doi: 10.1007/s11709-023-0937-2

摘要： The interactions between reinforced concrete (RC) frames and infill walls play an important role in the seismic response of frames, particularly for low-rise frames. Infill walls can increase the overall lateral strength and stiffness of the frame owing to their high strength and stiffness. However, local wall-frame interactions can also lead to increased shear demand in the columns owing to the compressive diagonal strut force from the inll wall, which can result in failure or in serious situations, collapse. In this study, the effectiveness of a design strategy to consider the complex infill wall interaction was investigated. The approach was used to design example RC frames with infill walls in locations with different seismicity levels in Thailand. The performance of these frames was assessed using nonlinear static, and dynamic analyses. The performance of the frames and the failure modes were compared with those of frames designed without considering the infill wall or the local interactions. It was found that even though the overall responses of the buildings designed with and without consideration of the local interaction of the infill walls were similar in terms the overall lateral strength, the failure modes were different. The proposed method can eliminate the column shear failure from the building. Finally, the merits and limitations of this approach are discussed and summarized.

关键词： reinforced concrete frames     infill wall     seismic design method     shear failure     wall-frame interaction    

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标题 作者 时间 类型 操作

Energy absorption potential of concrete floors containing secondary (shrinkage and temperature) reinforcements

K. S. SIVAKUMARAN,R. M. KOROL,Xiao FAN

期刊论文

An improved low-complexity sum-product decoding algorithm for low-density parity-check codes

Michaelraj Kingston ROBERTS,Ramesh JAYABALAN

期刊论文

the ammonia oxidation capacity of ammonia-oxidizing archaeon originated from wastewater: Utilizing low-density

期刊论文

A low-density polyethylene composite with phosphorus-nitrogen based flame retardant and multi-walled

Yong Luo, Yuhui Xie, Renjie Chen, Ruizhi Zheng, Hua Wu, Xinxin Sheng, Delong Xie, Yi Mei

期刊论文

Correlative investigation of copper/low-density polyethylene nanocomposite on the endometrial angiogenesis

LI Jianxiong, LIU Zilong, DUAN Yonggang, YU Jing, ZHU Changhong, LI Shuang, XIE Changsheng

期刊论文

Performance of inverse fluidized bed bioreactor in treating starch wastewater

M. RAJASIMMAN, C. KARTHIKEYAN

期刊论文

Shear assessment of compression flanges of structural concrete T-beams

Bj?rn SCHüTTE,Viktor SIGRIST

期刊论文

混凝土结构性干预所必需的材料力学性能

Tamon Ueda

期刊论文

Comments on “Prediction on CO uptake of recycled aggregate concrete”, Frontiers of Structural and Civil

期刊论文

Design of packing cup interference fit value of hypercompressors for low density polyethylene production

Da LEI,Xuehong LI,Yun LI,Xiwen REN

期刊论文

Recent development in low-constraint fracture toughness testing for structural integrity assessment of

Jidong KANG, James A. GIANETTO, William R. TYSON

期刊论文

Evaluation of the static and dynamic structural performance of segmental pre-stressed concrete box girder

Ali Fadhil NASER, Zonglin WANG

期刊论文

On the added value of multi-scale modeling of concrete

期刊论文

Crack detection for wading-concrete structures using water irrigation and electric heating

期刊论文

Performance evaluation of low-rise infilled reinforced concrete frames designed by considering local

期刊论文